(a) Field of the Invention
The present invention relates to a thin film transistor (TFT) array panel and a method of manufacturing the same.
(b) Description of the Related Art
A liquid crystal display (LCD) is one of the most widely used flat panel displays (FPD). An LCD includes two substrates on which electrodes are formed and a liquid crystal layer that is interposed therebetween so that a voltage is applied to the electrodes to re-arrange the liquid crystal molecules of the liquid crystal layer and thereby control the amount of transmitted light.
Among the various types of LCDs, an LCD in which field generating electrodes are provided in two display panels is mainly used. In this type of LCD, a plurality of pixel electrodes are arranged in a matrix on one display panel (hereinafter, referred to as a thin film transistor array panel) and the other display panel (hereinafter, referred to as a common electrode panel) is covered with one common electrode. Different voltages are respectively applied to the pixel electrodes in the LCD, to display an image. Therefore, thin film transistors (TFT) are formed in the display panel for switching the voltages applied to the pixel electrodes. The TFTs have three terminal elements respectively connected to the pixel electrodes, gate lines for transmitting signals for controlling the TFTs, and data lines for transmitting the voltages to be applied to the pixel electrodes.
The TFTs operate as switching elements for transmitting the image signals transmitted through the data lines to the pixel electrodes or for preventing the image signals transmitted through the data lines from being transmitted to the pixel electrodes in accordance with scanning signals transmitted through the gate lines.
A TFT array panel includes a conductive layer including the gate lines and the data lines, and a plurality of thin films including a semiconductor layer and an insulation layer. Each of the thin films is patterned using a separate mask.
As each mask is sequentially added, photosensitive layer application, exposure, development, and cleaning processes must be repeated so that time and cost required for the processes remarkably increase. Therefore, it is desirable to reduce the number of masks used to increase efficiency and reduce cost. Consequently, a method of etching a metal data layer and a semiconductor layer with one mask is suggested.
Furthermore, the entire metal data layer of a typical TFT resides on the upper surface of the semiconductor layer and the semiconductor layer protrudes from the sides of the metal data layer. Therefore, areas of the semiconductor layer that are exposed to the light supplied by a light source increase so that photo leakage current increases and deteriorates the characteristics of the TFTs, which results in an after image that can be recognized. Consequently, an advantageous structure and method for reducing after images are suggested.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.